In forming a semiconductor device, as a method for forming an ohmic contact between a gate electrode and source/drain and a metal line, silicide by means of a combination of a metal and a compound of silicon is used.
Currently, the material commonly applied to a device in 0.18 μm technology and below is cobalt (Co). Here, cobalt is combined in a CoSi2 form that shows a relatively low silicide resistance Rsh and a good RC operation of the ohmic contact between the metal and the gate and the source/drain.
Generally, the process of forming CoSi2 includes performing a cobalt deposition, forming a capping layer of TiN on the deposited cobalt and then subjecting the wafer to a rapid thermal processing (RTP).
Herein, the reason why the capping TiN is used is because Co is very easily oxidized in the air, so that if material of the substrate not directly reacted with Co is capped, oxidation is prevented and silicide is thus well formed.
However, in the related art, the capping TiN layer material uses crystalline TiN material deposited by a physical vapor deposition (PVD).
However, the crystalline TiN has a columnar structure so that air is diffused according to the columnar structure and is able to oxidize the Co. The oxidized Co may cause a defect in the device by not exhibiting a normal silicide operation.